Brushless motor commutation and control

Abstract

A commutation apparatus drives a brushless motor having a stator equipped with a plurality of coils and a rotor. The commutation apparatus comprises a rotatable commutator shaft, two or more conducting rings carried discretely about the shaft, and two or more conducting segments carried discretely about the shaft at staggered positions along or near a plane perpendicularly intersecting the shaft. Each conducting segment is electrically connected to one of the conducting rings. Two or more electrical source contacts are provided for rotatably connecting a power supply across pairs of the conducting rings. A plurality of electrical load contacts is further provided for sequentially, rotatably connecting the conducting segments to discrete coils of the brushless motor. In particular embodiments of the commutation apparatus, a magnetic coupling is employed for rotatably coupling the commutator shaft to the rotor of the brushless motor, and a pressure-bearing container is provided for rotatably supporting the commutator shaft and the coupling therein.

1. A downhole tool comprising:
 a commutation apparatus for a brushless motor having a stator equipped with a plurality of coils and a rotor equipped with a permanent magnet assembly, the commutation apparatus comprising:
 a rotatable commutator shaft; 
 two or more conducting rings carried discretely about the shaft; 
 two or more conducting segments carried discretely about the shaft at staggered positions along or near a plane perpendicularly intersecting the shaft, each conducting segment being electrically connected to one of the conducting rings; 
 two or more electrical source contacts for rotatably connecting a power supply across pairs of the conducting rings; and 
 a plurality of electrical load contacts for sequentially, rotatably connecting the conducting segments to discrete coils of the brushless motor. 
 
 
   
   
     2. The downhole tool of  claim 1 , further comprising a coupling at least partially carried by the commutator shaft for rotatably coupling the commutator shaft to the rotor of the brushless motor. 
   
   
     3. The downhole tool of  claim 2 , wherein the coupling comprises a magnetic coupling element carried by the commutator shaft that complements a magnetic coupling element carried by the rotor of the brushless motor. 
   
   
     4. The downhole tool of  claim 2 , further comprising a container for rotatably supporting the commutator shaft and the coupling therein. 
   
   
     5. The downhole tool of  claim 4 , wherein the container is adapted for withstanding downhole fluid pressure within a wellbore penetrating a subsurface stratum. 
   
   
     6. The downhole tool of  claim 4 , wherein the electrical source contacts comprise spring-loaded brushes carried within the container about the commutator shaft for establishing continuous electrical connections with the respective conducting rings. 
   
   
     7. The downhole tool of  claim 4 , wherein the electrical load contacts comprise spring-loaded brushes carried within the container about the commutator shaft for establishing staggered electrical connections with the respective conducting segments along or near the plane. 
   
   
     8. The downhole tool of  claim 1 , wherein the brushless motor is a two-pole motor. 
   
   
     9. The downhole tool of  claim 8 , comprising:
 two conducting rings carried discretely about the commutator shaft; 
 two conducting segments carried discretely about the commutator shaft at staggered positions along or near a plane perpendicularly intersecting the commutator shaft, each conducting segment being electrically connected to one of the conducting rings; 
 two electrical source contacts for rotatably connecting a power supply across the conducting rings; and 
 six electrical load contacts for sequentially, rotatably connecting the two conducting segments to two discrete coils of the brushless motor. 
 
   
   
     10. The downhole tool of  claim 1 , wherein the brushless motor is a four-pole motor. 
   
   
     11. The downhole tool of  claim 1 , comprising:
 five conducting rings carried discretely about the commutator shaft; 
 four sets of four conducting segments carried discretely about the commutator shaft at staggered positions along or near four respective planes perpendicularly intersecting the commutator shaft, each conducting segment being electrically connected to one of the conducting rings; 
 twelve electrical source contacts for rotatably connecting a power supply across pairs of the conducting rings; and 
 twelve electrical load contacts for sequentially, rotatably connecting pairs of the conducting segments to two or more discrete coils of the brushless motor. 
 
   
   
     12. The downhole tool of  claim 1 , wherein the downhole tool is a borehole inspection tool. 
   
   
     13. The downhole tool of  claim 1 , wherein the downhole tool is a casing inspection tool. 
   
   
     14. The downhole tool of  claim 1 , wherein the downhole tool is a downhole fluid sampling tool. 
   
   
     15. The downhole tool of  claim 1 , wherein the downhole tool is a downhole formation pressure measurement tool. 
   
   
     16. The downhole tool of  claim 1 , wherein the downhole tool is a downhole formation sampling tool. 
   
   
     17. The downhole tool of  claim 1 , wherein the downhole tool is a downhole casing driller tool. 
   
   
     18. The downhole tool of  claim 1 , wherein the downhole tool is a downhole mechanical services tool. 
   
   
     19. The downhole tool of  claim 1 , wherein the downhole tool is a downhole rotary steerable tool. 
   
   
     20. The downhole tool of  claim 1 , wherein the downhole tool is an electrical submersible pump. 
   
   
     21. The downhole tool of  claim 1 , wherein the downhole tool is a flow control device.